Mechanism regulating telomerase activity in Oryza sativa L.

A stretch PCR-based method used to measure human telomerase activity was modified for use with plant telomerase and shown to be useful for quantitative analysis. We isolated a full-length cDNA of a telomerase reverse transcriptase catalytic subunit gene from suspension-cultured cells of rice (Oryza sativa L.). A single copy of this gene is present in the rice genome. Telomerase activity was detected in suspension-cultured O. sativa cells at all growth stages, although the activity was greatest in 2-day-old subcultures and decreased at 6 days. Nevertheless, the accumulation of O. sativa telomerase mRNA was nearly constant in cells at all growth stages. Although no telomerase activity was detected in the lower portions of blades in 3-month-old rice plants, telomerase mRNA accumulated in the blades. Tests of different tissues excised from rice seedlings 3 weeks after sowing showed that root tips had high telomerase activity, while roots without root tips had no telomerase activity. Nevertheless, telomerase mRNA accumulated in both tissues. These results suggest that telomerase activity in tissues of O. sativa is regulated at the post-transcriptional or post-translational levels.